As examples of an absorbent article that absorbs fluid, disposable diapers, sanitary napkins, and the like are used. These absorbent articles include an absorbent body 1 that is produced by forming pulp fibers into a predetermined shape.
The absorbent body 1 is formed by a fiber stacking apparatus 10a in a production line. FIG. 1 is a side view of the fiber stacking apparatus 10a partially shown in a vertical cross-section. The fiber stacking apparatus 10a includes as the main body a rotating drum 20 that rotates in a circumferential direction Dc, and recessed form dies 21 are formed on an outer circumferential surface 20a of the rotating drum 20. And a bottom section of the form dies 21 are configured so that air intake is possible. Moreover, a distribution opening 31a of a duct 31 is provided so as to face the outer circumferential surface 20a of the rotating drum 20, and from the distribution opening 31a an air mixture 3 with the pulp fibers 2 mixed in is discharged toward the outer circumferential surface 20a. 
Thus, in the case of the form die 21 passing the position of the distribution opening 31a as the rotating drum 20 rotates, the air mixture 3 discharged from the distribution opening 31a is sucked through the bottom section of the form die 21. And by suction forces generated inside the form die 21 in this way, the pulp fibers 2 in the air mixture 3 are stacked inside the form die 21 and thus formed into the absorbent body 1 (see PTL 1).